Recreational drug use is the use of mind-altering substances for the purpose of altering one's mental state, without the supervision of a physician. The majority of human societies throughout history have each held a tradition of recreational drug use in various forms, well known examples being most of Europe and the Americas' love for alcohol, the once high popularity of opium in Asia, and presence of cannabis in virtually every culture throughout recorded history.

Some recreational drugs are addictive, some are at least somewhat harmful to health, and in many cases their possesion and use violate the law. Although in some liberal cultures drug use is now looked upon as being an act of responsible adult behavior. Recognized use of cannabis as an aid for illness has led to increased awareness about the helpfullness of this illegal substance. Recreational drugs are used in the USA by as much as 80% of the population according to several recent polls. Given this high popularity, many societies have resorted to harm reduction by informing users of ways to reduce common risks associated with popular drugs, and providing assistance for drug users who wish to stop using.